Light-emitting device

• US 7,129,917 B2
• Filed: 06/23/2003
• Issued: 10/31/2006
• Est. Priority Date: 02/29/2000
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun, Yamazaki, Shunpei, Osada, Mai
• Primary Examiner(s): Wu, Xiao
• Assistant Examiner(s): LESPERANCE, JEAN E
• Application Number:
  US10/600,866
• Publication Number:
  US 20040080470A1
• Time in Patent Office: 1,226 Days
• Field of Search: 345/77, 345/78, 345/79, 345/76, 313/498, 313/500, 313/505
• US Class Current: 345/77
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3275 Details of drivers for data electrodes
• CPC Class Codes: H01L 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 27/1222 with a particular composition, shape or crystalline structure of the active layer
• CPC Class Codes: H01L 27/1251 comprising TFTs having a different architecture, e.g. top- and bottom gate TFTs
• CPC Class Codes: H01L 27/1296 adapted to increase the uniformity of device parameters
• CPC Class Codes: H01L 29/42384 for thin film field effect transistors, e.g. characterised by the thickness or the shape of the insulator or the dimensions, the shape or the lay-out of the conductor
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H01L 29/78621 with LDD structure or an extension or an offset region or characterised by the doping profile
• CPC Class Codes: H01L 29/78627 : with a significant overlap between the lightly doped drain and the gate electrode, e.g. GOLDD
• CPC Class Codes: H01L 29/78654 : Monocrystalline silicon transistors
• CPC Class Codes: H01L 29/7866 : Non-monocrystalline silicon transistors
• CPC Class Codes: H01L 29/78672 : Polycrystalline or microcrystalline silicon transistor
• CPC Class Codes: H01L 29/78696 : characterised by the structure of the channel, e.g. multichannel, transverse or longitudinal shape, length or width, doping structure, or the overlap or alignment between the channel and the gate, the source or the drain, or the contacting structure of the channel H01L29/78612 takes precedence; transistors having a drain offset region or a lightly doped drain [LDD] H01L29/78621
• CPC Class Codes: H10K 50/805 : Electrodes
• CPC Class Codes: H10K 59/00 : Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
• CPC Class Codes: H10K 59/12 : Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/1201 : Manufacture or treatment
• CPC Class Codes: H10K 59/1213 : the pixel elements being TFTs
• CPC Class Codes: H10K 59/1216 : the pixel elements being capacitors
• CPC Class Codes: H10K 59/123 : Connection of the pixel electrodes to the thin film transistors [TFT]
• CPC Class Codes: H10K 59/124 : Insulating layers formed between TFT elements and OLED elements
• CPC Class Codes: H10K 59/35 : comprising red-green-blue [RGB] subpixels
• CPC Class Codes: H10K 59/871 : Self-supporting sealing arrangements
• CPC Class Codes: H10K 59/8722 : Peripheral sealing arrangements, e.g. adhesives, sealants

Abstract

There is provided an EL light-emitting device with less uneven brightness. When a drain current of a plurality of current controlling TFTs is Id, a mobility is μ, a gate capacitance per unit area is Co, a maximum gate voltage is Vgs_(max), a channel width is W, a channel length is L, an average value of a threshold voltage is Vth, a deviation from the average value of the threshold voltage is ΔVth, and a difference in emission brightness of a plurality of EL elements is within a range of ±n %, a semiconductor display device is characterized in that

$\begin{array}{c}A=\frac{2Id}{\mu *C_0}\\ \frac{A}{{\left({\mathrm{Vgs}}_{\left(\max \right)}-\mathrm{Vth}\right)}^2}\leqq \frac{W}{L}\leqq {\left(\sqrt{1+\frac{n}{100}}-1\right)}^2*\frac{A}{\Delta {\mathrm{Vth}}^2}\\ \Delta \mathrm{Vth}\leqq \left(\sqrt{1+\frac{n}{100}}-1\right)*\sqrt{A*L/W}\end{array}$

Claims

1. A driving method of a light-emitting device comprising:

at least one frame period including at least one line period, the line period comprising;

selecting a gate signal line connected to switching TFTs by inputting a selection signal from a gate signal line driving circuit,

inputting a video signal to each of source signal lines from a source signal line driving circuit, and

inputting the video signal inputted to each of the source signal lines to a gate electrode of each of current controlling TFTs through each of the switching TFTs,

wherein an emission brightness of each of EL elements is controlled by the video signal inputted to the gate electrode of each of the current controlling TFTs, and

wherein a drain current of each of the current controlling TFTs when the emission brightness of the EL element becomes maximum is Id, a mobility is μ

, a gate capacitance per unit area is C₀, a maximum gate voltage is Vgs_(max), a channel width is W, a channel length is L, an average value of a threshold voltage is Vth, a deviation from the average value of the threshold voltage is Δ

Vth, and a difference in the emission brightness of each of the EL elements is within a range of ±

n %,

2. A method according to claim 1, wherein the emission brightness of each of the plurality of EL elements is within a range of ±

5%.

3. A method according to claim 1, wherein the maximum gate voltage is 25 V.

4. A method according to claim 1, wherein the maximum gate voltage is 25 V and a ratio of the channel width W to the channel length L of each of the plurality of current controlling TETs is 2.26×

10<sup>−

3</sup>≦

W/L≦

0.214.

5. A method according to claim 1, wherein the gate capacitance is formed in a portion where the channel forming region, the gate insulating film, and the gate electrode overlap with one another in each of the current controlling TFTs.

6. A video camera using the driving method of the light-emitting device of claim 1.

7. An image reproduction apparatus using the driving method of the light-emitting device of claim 1.

8. A head mount display using the driving method of the light-emitting device of claim 1.

9. A personal computer using the driving method of the light-emitting device of claim 1.

10. A driving method of a light-emitting device comprising:

at least one frame period including at least one line period, the line period comprising;

selecting a gate signal line connected to switching TFTs by inputting a selection signal from a gate signal line driving circuit,

inputting a video signal to each of source signal lines from a source signal line driving circuit, and

inputting the video signal inputted to each of the source signal lines to a gate electrode of each of current controlling TFTs through each of the switching TFTs,

wherein a power supply line connected to each of the current controlling TFTs is kept a constant potential,

wherein an emission brightness of each of EL elements is controlled by the video signal inputted to the gate electrode of each of the current controlling TFTs, and

wherein a drain current of each of the current controlling TFTs when the emission brightness of the EL element becomes maximum is Id, a mobility is μ

, a gate capacitance per unit area is C₀, a maximum gate voltage is Vgs_(max), a channel width is W, a channel length is L, an average value of a threshold voltage is Vth, a deviation from the average value of the threshold voltage is Δ

Vth, and a difference in the emission brightness of each of the EL elements is within a range of ±

n %,

11. A method according to claim 10, wherein the emission brightness of each of the plurality of EL elements is within a range of ±

5%.

12. A method according to claim 10, wherein the maximum gate voltage is 25 V.

13. A method according to claim 10, wherein the maximum gate voltage is 25 V and a ratio of the channel width W to the channel length L of each of the plurality of current controlling TFTs is 2.26×

10<sup>−

3</sup>≦

W/L≦

0.214.

14. A method according to claim 10, wherein the gate capacitance is formed in a portion where the channel forming region, the gate insulating film, and the gate electrode overlap with one another in each of the current controlling TFTs.

15. A video camera using the driving method of the light-emitting device of claim 10.

16. An image reproduction apparatus using the driving method of the light-emitting device of claim 10.

17. A head mount display using the driving method of the light-emitting device of claim 10.

18. A personal computer using the driving method of the light-emitting device of claim 10.

19. A driving method of a light-emitting device comprising:

at least one frame period including at least one fine period, the line period comprising;

selecting a gate signal line connected to switching TFTs by inputting a selection signal from a gate signal line driving circuit,

inputting a video signal to each of source signal lines from a source signal line driving circuit, and

inputting the video signal inputted to each of the source signal lines to a gate electrode of each of current controlling TFTs through each of the switching TFTs,

wherein an emission brightness of each of EL elements is controlled by the video signal inputted to the gate electrode of each of the current controlling TFTs, and

wherein a drain current of each of the current controlling TFTs when the emission brightness of the EL element becomes maximum is Id, a mobility is μ

, a gate capacitance per unit area is C₀, a maximum gate voltage is Vgs_(max), a channel width is W, a channel length is L, an average value of a threshold voltage is Vth, a deviation from the average value of the threshold voltage is Δ

Vth, and a difference in the emission brightness of each of the EL elements is within a range of ±

n %,

20. A method according to claim 19, wherein the emission brightness of each of the plurality of EL elements is within a range of ±

5%.

21. A method according to claim 19, wherein the maximum gate voltage is 25 V.

22. A method according to claim 19, wherein the maximum gate voltage is 25 V and a ratio of the channel width W to the channel length L of each of the plurality of current controlling TFTs is 2.26×

10<sup>−

3</sup>≦

W/L≦

0.214.

23. A method according to claim 19, wherein the gate capacitance is formed in a portion where the channel forming region, the gate insulating film, and the gate electrode overlap with one another in each of the current controlling TFTs.

24. A video camera using the driving method of the light-emitting device of claim 19.

25. An image reproduction apparatus using the driving method of the light-emitting device of claim 19.

26. A head mount display using the driving method of the light-emitting device of claim 19.

27. A personal computer using the driving method of the light-emitting device of claim 19.

28. A driving method of a light-emitting device comprising:

at least one frame period including at least one line period, the line period comprising;

selecting a gate signal line connected to switching TFTs by inputting a selection signal from a gate signal line driving circuit,

inputting a video signal to each of source signal lines from a source signal line driving circuit, and

inputting the video signal inputted to each of the source signal lines to a gate electrode of each of current controlling TFTs through each of the switching TFTs,

wherein a power supply line connected to each of the current controlling TFTs is kept a constant potential,

wherein an emission brightness of each of EL elements is controlled by the video signal inputted to the gate electrode of each of the current controlling TFTs, and

wherein a drain current of each of the current controlling TFTs when the emission brightness of the EL element becomes maximum is Id, a mobility is μ

, a gate capacitance per unit area is C₀, a maximum gate voltage is Vgs_(max), a channel width is W, a channel length is L, an average value of a threshold voltage is Vth, a deviation from the average value of the threshold voltage is Δ

Vth, and a difference in the emission brightness of each of the EL elements is within a range of ±

n %,

29. A method according to claim 28, wherein the emission brightness of each of the plurality of EL elements is within a range of ±

5%.

30. A method according to claim 28, wherein the maximum gate voltage is 25 V.

31. A method according to claim 28, wherein the maximum gate voltage is 25 V and a ratio of the channel width W to the channel length L of each of the plurality of current controlling TFTs is 2.26×

10<sup>−

3</sup>≦

W/L≦

0.214.

32. A method according to claim 28, wherein the gate capacitance is formed in a portion where the channel forming region, the gate insulating film, and the gate electrode overlap with one another in each of the current controlling TFTs.

33. A video camera using the driving method of the light-emitting device of claim 28.

34. An image reproduction apparatus using the driving method of the light-emitting device of claim 28.

35. A head mount display using the driving method of the light-emitting device of claim 28.

36. A personal computer using the driving method of the light-emitting device of claim 28.